1. Field of the Invention
The present invention relates to a resin-encapsulated power semiconductor module by transfer molding having excellent productivity, and more particularly, to a resin-encapsulated power semiconductor module by transfer molding that achieves a size reduction and high reliability and a manufacturing method thereof.
2. Background Art
A power semiconductor module generally operates at a large current and a high voltage. It is therefore essential to release heat generated in association with the operation efficiently to the outside of the power semiconductor module. To this end, the power semiconductor module is formed by encapsulating components including power semiconductor elements, an insulating substrate with wiring pattern, a metal base plate, and external terminal connection bodies with transfer mold resin.
Performance requirements of the power semiconductor module as above are to reduce thermal resistance and ensure high insulation qualities. Moreover, it is crucial to achieve a size reduction and high reliability.
As means for achieving a size reduction for the resin-encapsulated power semiconductor module by transfer molding, it has been proposed to expose the top portion of an electrically conductive tubular external terminal connection body to the surface of the top face of the resin encapsulated region by transfer molding.
A resin-encapsulated power semiconductor module by transfer molding disclosed, for example, in JP-A-2007-184315 has power semiconductor elements that switch a current, an insulating substrate with circuit pattern to which the power semiconductor elements are bonded and electrically connected, a metal base to which the insulating substrate with circuit pattern is bonded. Tubular female connectors to be connected to the external terminal are exposed to the surface of the top face of the resin encapsulated region by transfer molding of the insulating substrate with circuit pattern. A groove is formed on the surface of the metal base in the vicinity of the periphery of the insulating substrate with circuit pattern. The insulating substrate with circuit pattern together with the groove formed on the metal base surface is encapsulated with resin by transfer molding. The encapsulated region is on the inner side of the outermost peripheral region of the metal base. In other words, it is configured in such a manner that the outer peripheral portion on the outside of the encapsulated region of the metal base is exposed, and attachment holes for cooling fins attached to the backside of the metal base are provided to the exposed portion in the outer peripheral portion of the metal base.
The power semiconductor module of the cited reference is configured in such a manner that the surface of the top portion of the tubular female connector is exposed to the surface of the top face of the encapsulated region. Accordingly, the external terminal is inserted into the female connector. Owing to this structure, a size of the power semiconductor module encapsulated with transfer mold resin can be reduced.
Also, the configuration to expose all the external terminal connection bodies to the surface of the top face of the encapsulated region with transfer mold resin so as to be extracted from the top face is advantageous over a power semiconductor module encapsulated with transfer mold resin of a laterally protruding external terminal structure using a typical lead frame in that not only the size can be reduced but also the manufacturing steps can be simpler.
Further, forming the groove in the metal base provides a penetration effect of the encapsulation resin. At the same time, adhesion properties can be enhanced by a stress mitigation effect provided by applying polyamide resin. Consequently, because peeling is suppressed, it is possible to obtain a power semiconductor module capable of enhancing the reliability.
In the power semiconductor module in the related art, the top portions of all the external terminal connection bodies are placed so as to be exposed to the surface of the top face of the encapsulated region. This configuration makes it possible to place the external terminals so that they can be extracted within the top face of the encapsulated region and is therefore advantageous in reducing the size. However, because the attachment holes for the cooling fins made in the metal base are provided on the outside of the encapsulated region, the external terminal connection bodies cannot be provided in the exposed metal base region. Hence, there is a problem that it is difficult to reduce the size of the overall power semiconductor module because of the area of the exposed metal base.
In addition, it is necessary to form the groove in the metal base in order to obtain the peeling suppression effect by enhancing the adhesion properties between the metal base and the encapsulation resin, and it is also necessary to apply special processing, such as applying polyamide resin. The manufacturing costs are consequently increased.
Further, a warping condition, that is, elastic deformation at a given position differs between the metal base in the encapsulated region and the metal base exposed on the outside of the encapsulated region. This poses a problem that it becomes difficult to obtain high reliability.